Catheters are flexible medical instruments used for withdrawal and/or introduction of fluids to and from body cavities, ducts, and vessels. Catheters have particular application in hemodialysis procedures, in which blood is withdrawn from a blood vessel for treatment and subsequently returned to the blood vessel for circulation through a patient's body.
Many hemodialysis catheters include multiple lumens, such as dual or triple-lumen catheters. One lumen is dedicated to withdrawal of fluid from a vessel, and at least one other lumen is dedicated to return of fluid to the vessel. Generally, the lumen through which fluid is withdrawn is referred to as the “arterial” lumen, and the lumen through which fluid is returned is referred to as the “venous” lumen. During a hemodialysis procedure, after placement of a multiple lumen catheter in a patient, blood is typically withdrawn from the patient through the arterial lumen of the catheter, and is directed to a hemodialysis unit for dialysis to remove waste and toxins from the blood. The dialyzed blood is then returned to the patient through the venous lumen of the catheter.
Generally, hemodialysis catheters are categorized as either acute or chronic. Acute catheters are designed to be placed in a patient under emergent circumstances, under which delays in placement are unacceptable. Acute catheters typically remain in place for only a few days. Chronic catheters, by comparison, typically remain in place for extended periods of time, and may be implanted via surgical dissection, which can be performed at the patient's bedside or in an ambulatory surgical setting.
Catheters, particularly chronic dialysis catheters, may be subject to thrombus formations following placement. These thrombus formations can restrict or block blood flow through the catheter, potentially lengthening the time required for treatment, compromising the efficacy of the treatment, and/or requiring more frequent replacement of the catheter. Methods of dislodging thrombus formations to restore proper fluid flow include forcing a solution through the catheter and/or, in the case of dialysis catheters, reversing the lines of the dialysis machine. Such treatments can be limited by the amount of fluid pressure that can be built up in the catheter. Moreover, such treatments can have limited efficacy in catheters with multiple openings, such as catheters with distal and side openings, because fluids moving through the catheter tend to bypass those openings with more significant blockages and exit through those openings that offer less resistance to flow.